Chlorpheniramine is a potent, short-acting antihistamine. Chlorpheniramine's antihistamine pharmacodynamic action substantially diminishes or abolished the action of histamine in the body. Chlorpheniramine achieves these results by occupying the receptor sites, mainly the H-1 receptor sites, in the effector cells to the exclusion of histamine. The antihistamine chlorpheniramine is thus an H-1 receptor antagonists.
Chlorpheniramine is indicated therapeutically for the pallative treatment of allergic reactions. Chlorpheniramine is indicated for the relief of asthma, for the relief of symptoms of seasonal hay fever, for nasal irritation and discharge, for the management of uticaria, skin irritations, pruritus ani, contact dermatitis, insect bites, and the like.
The prior art administered chlorpheniramine orally because chlorpheniramine is well-absorbed following oral administration. A common fault with the prior art dosage forms used for oral administration is that they do not deliver chlorpheniramine at a rate controlled by the dosage form. For example, chlorpheniramine is released from one prior art dosage form by leaching from minute pellets coated with complex digestible substances, at a rate dependent on the volume of fluid present in the environment of use. This kind of release is not rate controlled by a dosage form.
In the light of the above presentation, it will be appreciated by those versed in the dispensing art that a pressing need exists for a novel dosage form that can deliver chlorpheniramine at a rate controlled by the dosage form. The need exists also for a dosage form that can deliver chlorpheniramine for obtaining its beneficial effects over a prolonged period of time.